#225 Parsing with Ruby

About techniques for working with XML, HTML4, and HTML5 from Ruby with gems like nokogiri.

Notes

While XML and HTML is just text and so possible to work with it as string data, better to use a gem that can handle all those cases like validation, encoding and semantic searching.

Nokigiri

Nokogiri (鋸) is the most popular tool for working with XML, HTML4, and HTML5 from Ruby.

HTML with Nokogiri

The Nokogiri::XML class provides entry point for XML parsing:

source = 'https://nokogiri.org/tutorials/installing_nokogiri.html'
Nokogiri::HTML(URI.open(source))

See nokogiri_html_test.rb for test examples of HTML parsing, including for example:

• find by css doc.css('nav ul.menu li a', 'article h2')
• find by xpath doc.xpath('//nav//ul//li/a', '//article//h2')
• find with search doc.search('nav ul.menu li a', '//article//h2')

$ ./nokogiri_html_test.rb
Run options: --seed 3738

# Running:

...

Finished in 1.076714s, 2.7863 runs/s, 5.5725 assertions/s.

3 runs, 6 assertions, 0 failures, 0 errors, 0 skips

XML with Nokogiri

The Nokogiri::XML class provides entry point for XML parsing:

source_file = Pathname.new(File.dirname(__FILE__)).join('data', 'planes.xml')
Nokogiri::XML(File.open(source_file))

See nokogiri_xml_test.rb for test examples of XML parsing, including for example:

• find by element name doc.xpath("//model")
• find by element attribute value doc.xpath(%(//seller[@phone="555-222-3333"]))
• find by element has child doc.xpath(%(//ad[price]))

$ ./nokogiri_xml_test.rb
Run options: --seed 60440

# Running:

...

Finished in 0.002498s, 1200.9608 runs/s, 2802.2419 assertions/s.

3 runs, 7 assertions, 0 failures, 0 errors, 0 skips

Credits and References

• Nokogiri (鋸) - main site
• nokogiri - rubygems
• nokogiri - api doc
• XML Samples files - borrowed from The University of Texas at Austin CS329 2010
• Xpath cheatsheet